1. Field of the Invention
This invention relates to a bandsaw blade and, more specifically, to a bandsaw having teeth with bodies of a generally uniform height and wherein at least some of the teeth have a cutting extension extending above the height of the teeth.
2. Background Information
Bandsaw blades include a flat body having a plurality of teeth extending therefrom. Each tooth has a height, extending above the body, a width, which is perpendicular to the longitudinal axis of the body, and a length, extending along the longitudinal axis of the body. Typically, the bandsaw body is made from a material such as steel and a carbide tip, which includes the cutting edge, is coupled to the tip of each tooth. The bandsaw blade moves in the longitudinal direction of the body in a single direction, hereinafter “the cutting path.” Each tooth also has a cutting edge located, generally, at the greatest height on the tooth. As the moving bandsaw blade comes into contact with a workpiece, the teeth cut a channel in the workpiece.
A bandsaw blade is more efficient if the load due to cutting forces, hereinafter “cutting load,” is distributed across a group of teeth. As used herein, a “group” of teeth is a pattern of teeth that is repeated along the length of the bandsaw blade. To improve the efficiency of the bandsaw blade, teeth having different shapes are disposed on the body in groups. The groups each have the teeth of different shapes disposed in the same pattern. Thus, the groups are described as “repeating” groups. Each tooth in a group is structured to cut a different portion of the channel in the workpiece. In prior art bandsaw blades the teeth were structured to cut a different portion of the channel in one of two ways; set teeth, which are each tilted differently, or unset teeth which have variations in the tooth height and width.
The first means of distributing the cutting load is to have set teeth. That is, as shown in FIG. 1, some of the generally rectangular teeth in a group are set, or tilted, to the left or right of the cutting path. Thus, assuming a group of three teeth, each tooth 1A, 1B, 1C is disposed on a body 2. The first tooth 1A in the group is un-set, that is, not tilted. The first tooth 1A in the group cuts the middle portion of the channel. The second tooth 1B is tilted to the left. As such, the second tooth 1B left edge cuts the left portion of the channel. At the same time, the right edge of the second tooth 1B, which, because of the tilt, is higher than the first tooth, cuts within the center of the channel. The third tooth 1C is tilted to the right. The right edge of the third tooth 1C cuts the right portion of the channel while the left edge of the third tooth 1C also cuts within the center portion of the channel. As such the cutting load is distributed over the three teeth in the group. Of course, there may be more than three teeth in the group and various patterns of set teeth.
The second means of distributing the cutting load is to have a group of un-set teeth each with an inverse height-width ratio. That is, as shown in FIG. 2, a tooth may be tall and thin 3A, short and wide 3C, or somewhere in between 3B. Working again with a three tooth group for example, the first tooth 3A is the tallest, that is, extending the greatest distance from body 2, and has a cutting edge that is ⅓ the width of the channel. Thus, the first tooth 3A cuts the middle ⅓ of the channel. The second tooth 3B is shorter than the first tooth and is ⅔ the width of the channel. As such, the second tooth 3B widens the channel initially cut by the first tooth 3A. That is, the middle portion of the second tooth 3B travels in the groove cut by the first tooth 3A. The outer portions of the second tooth 3B, each of which is ⅙ the width of the channel, each cut a portion of the channel in the workpiece. Finally, the third tooth 3C is the shortest tooth and is as wide as the channel. As the first tooth 3A cuts the middle third portion of the channel and the second tooth 3B cuts an additional one sixth portion of the channel on each side (⅙+⅙=⅓), of channel cut by the first cut by the first tooth 3A, the third tooth 3C only has to cut the outer most portion on both sides of the channel. The portion cut by each outer edge of the third tooth 3C is one sixth the width of the channel (⅙+⅙=⅓). Thus, each tooth carries an equal portion of the cutting load. Again, this structure can be used with more than three teeth in a group.
Additionally, a bandsaw blade may groups of teeth that include sub groups. That is, a primary group may have two or more sub-groups of teeth. For example, a primary group may have a first sub-group of three teeth followed by a second sub-group of 5 teeth. Thus, the primary group is repeated along the bandsaw blade body in a 3-tooth, 5-tooth pattern.
Both of these means of distributing the cutting load suffer from disadvantages. For example, the cutting load on a set tooth creates a force that acts in a direction perpendicular to the angle of the set. That is, while in use, the set teeth are biased into alignment with the bandsaw body. This stress causes the bandsaw blade to wear out before the useful life of the cutting edges is exhausted. Unset teeth having different heights may experience different loads if the workpiece is fed too quickly. That is, if the workpiece is fed too rapidly, the taller teeth will be forced to cut a deeper chip than the shorter teeth. Thus, although the cutting edges on each tooth have an equal width, the cutting load is still different on each tooth. This leads to premature wear on the teeth carrying the greater load.
There is, therefore, a need for a bandsaw blade that evenly distributes the cutting load across all cutting teeth.
There is a further need for a bandsaw blade that is compatible with existing equipment.